I've had this puzzle on my phone for years. Every few months I'd glance at it and try and solve it. Last night, as I was eating dinner, I finally figured out the answer!

Ever play the game Myst? As a kid that's exactly how it was. Days of banging my head and then a rush of finally figuring something out. Really miss that

For everyone saying it's the difference between the two numbers, it's not it. Because the last one should be 8 to follow the rule

Figured it out. Weirdly, knowing you solved it made me confident I could too, and I don't even know you 🤔

::: spoiler spoiler I focused on the anomaly ignoring the rest, tried to see what possible rules could lead to it, then went back to see which rule also applied to the "non-anomalous" numbers.

---

:::

Non-bastardized version:

Hah, took me nearly a minute.

::: spoiler Tap for spoiler Add the digits on both sides.

? = 12 :::

But I only got it so quickly because I enjoyed a similar puzzle once.

1
11
21
1211
111221
312211
...

continue the series.

What the heck man I have things to do today.

I think I figured it out, but it's so easy that I don't think that could possibly be it. But it is, apparently.

Wow so easy, I got this in negative 4 second, literally 4 seconds before I even saw the puzzle. Of course I'm not going to share the solution here because I don't want to ruin It, but I definitely got it.

How do we know if we're right then?

Got it. Very misleading puzzle, haha.

Ah, typo is short for typographical error. I’v never realized that before.

I have to admit that I believe I have successfully found the solution.

It took me about 2 minutes lol.

The number of comments in this thread where people confidently declare they solved it with the wrong answer is absolutely baffling. Especially since it literally calls out the exception to that 'solution' in the post itself. Did those people not even look at the 7? That's the real strength of this puzzle, making idiots who think they're geniuses loudly prove their stupidity.

Took me about 20 minutes. There's a rule you find first that would work if the 7 was an 8. But it isn't. So there's another rule.

It took me several minutes but I finally got it. The comment saying to focus on the "anomaly" and how it could be 7 helped me to get there.

Yeah, feels pretty silly that I didn't see it sooner. I overcomplicated it haha.

I figured it out took about 10 minutes, thought i was onto it immediately until I had 8 at the end haha

I admit this one extended my toilet time more than I intended, but I got it!

Figured it out! That was cool, thanks!

::: spoiler Tap for spoiler Once I saw it and heard "the solution isn't obvious", I got focused on the idea of digital roots cuz I thought back to the game series 999. But that didn't work, so I focused on the shape of the pizzle and thought it looked like a thermometer, so I tried conversions of F to C, which also didn't work. But when I heard other people say that it made then think about the "obvious" solution and work around the 7, I thought back to my digital root idea and realized I was applying it in a different way in 999 versus what's happening here.

This was a fun adventure~ :::

Oh i see,

Its

::: spoiler solution 12

You add up the digits.

(7+2)+(9+9)=9+18=27

9+(4+5)=9+9=18

(1+8)+(3+9)=9+12=21

(2+1)+(3+6)=3+9=12

3+(2+8)=3+10=13

(1+3)+(2+1)=4+3=7

Yay :::

Got it in my first try! Thanks for making me feel extra smart today, though I think I'm just lucky. I recently watched a horror game with a similar one xD

That was a mean one. Adding another row at the top would expose it, though.

Wow, I just woke up and saved this to have a nice puzzle to work on for a while but I figured it out in like a minute... Kinda disappointed that happened to be honest.

I figured it out in about 3 minutes. I think I'm autistic or something

That was easy. Years, you say?

I think I figured it out but I always second guess myself lol. I feel like getting it on the first try means I am way off.

Dammit. I'm gonna have to stare at this for a few years now.

Thank you for the share. I will be back in three years time

Nice puzzle, at first you go "wtf last should be 8" but then I read the last sentence "not a typo" and took some minutes to crack it. If it wasn't for having seen a similar solution in a different puzzle I would have been completely lost and once you know the solution it's impossible to not see it. I can see how the author of the puzzle really liked it.

Being real, if this post hadn't made it clear that the solution was non obvious, I likely would have given up before getting it, just because my chicken is being more interesting than usual.

But, knowing that there was a "trick" to it, meaning that it takes some lateral thinking, I didn't take my usual approach to number puzzles, which means it only took one look at the upper left for the likely solution to be visible. Then it was just running down and testing with the rest, then plugging in for the solution.

No way in hell I would have had the patience for it when my baby bird is being a silly dinosaur without that front loading assumption the solution wouldn't be evident with a systematic approach. Oh, I'd have given it maybe fifteen minutes, but with a fuzzy butt in play, that would have been it

Oooh, sneaky but simple

Fun puzzle

I remember doing decision trees at Uni, and saw it immediately. Glad you got there OP.

Got it! Really cool puzzle. I used to enjoy solving puzzles like this, but nowadays I don't spend time in that.

I love puzzles like this—the rule always seems obvious after you see it. It’s satisfying when something that sits in the back of your mind for years finally clicks.

Got it. Nice puzzle.

First I figured out what was meant by the number 7 isn't a typo, by jumping to the wrong solution. Next I figured out the next idea was and it worked. No spoilers ༼⁠ᕗ⁠ຈ⁠ل͜⁠ຈ⁠༽⁠ᕗ

Solved it. Wonderful. I got really hung up on dividing things by nine and seven, trying to use the remainder and stuff. But the answer, as always, is far more obvious. That which we are so used to interpreting, we simply ignore it.

Holy shit got it!!!!!

I prime factored everything and was looking at ways to manipulate the factors together in a sensible rule. Seemed like a good approach, with the prime numbers at the end.

Now I'm a bit disappointed that ::: spoiler spoiler it was just the digits and not the factors... :::

Commenting for later (cheers OP)

Took me a few tries until I figured it out. It's cunningly misleading but it's not a trick puzzle (as I had suspected from some people's comments). There is a simple pattern.

Well, I got it correct with a guess based on a casual glance at what was there, not how the numbers actually relate or calculations based on rules or patterns.

Then I had to figure out how it actually worked.

Which was harder -- I wish I had kept scrolling.

Very elegantly designed puzzle :)

I still keep thinking it's 15, which I know is wrong, and then I math in 14,but I can't figure out a function. Does someone want to dm me or spoiler me the function how it works? My brain is too full of more important stuff and I cannot make room for this. But I must know!

I can give one hint if you want.

The solution reminded me of "Numerology". Which I am familiar with and probably why I was able to solve it in about a minute.

Thank you for posting this, it was exactly what I needed today and I didn't know it!!

Figured it out. Not sure what everyone means by a second obvious solution that doesn't work on the last one. My first solution that works on more than one works on all of them.

Fun puzzle - thanks for sharing!

I got it! 🎉

Ahaha that's so cheeky! Delightful

Don't search for creator of the puzzle, you will be instantly spoilered. At least some search engines return pictures with spoilers.

I’m afraid that this post has ruined my evening. I can’t figure it out and can’t let it go. I hate this.

Edit: I would not have survived if my life depended on my answer. I had to read through four to five people talking about methods until I noticed it. I’m really a stupid person.

Made me remember the extremely simple logic suite, a child could do it, but I had to sleep on it:

O T T F _

What's the letter after F ?

::: spoiler spoiler 12 :::

::: spoiler Displayed text here
Hidden text here
:::

IMHO, although it is hard to solve, it is neither brilliant nor profound - rather, it is misleading. It relies on a simple and common trickery involving multiple of 3, which is easy to see through for those with mathematical intuition. Of course many do not practice math, so it is seemingly interesting for them, but it's not much.

Why did you give the author a fake name?

::: spoiler Okay, I've got it. I suggest you take your time before revealing because it's quite satisfying if you figure it out yourself.

Each circle has something different inside it. You need to make sure the circle at the end of the arrow is different to the circle at the start of the arrow. This can be tricky because some circles have TWO arrows pointing at them, so it needs to be different to both things.

Interestingly this puzzle has multiple solutions. Here they are:

5, grape, Montreal, 97

Let me know if you find any others! :::

This kind of puzzle is very lazy for creators: just make the function more complicated and/or increase the amount of parameters and this makes the puzzle drastically more difficult.

The method of solving is just brute force. Boring. Uninspiring.

Found the answer in 1 minute. OK to post?

Figured it out in about 30 seconds. I’m no genius, guess I got lucky.

I let AI solve it for me now I feel confident that I'm much dumber than an AI.

15, right? You just add the left and bottom to get the right part

Edit: it was not 15 ;-;

Edit: sorry

Took me literally 4 seconds